Self contained metal casting dies

ABSTRACT

Metal die casting apparatus including three abutting plates of which the outside plates are movable relative to the center plate. The casting is formed in one plate and the gate for leading the molten metal to the casting is formed in the other plates. After forming the casting, the gate is broken off and ejected by movement of one end plate. The casting is then ejected by movement of the other end plate. The novel plate apparatus and the method of degating provides a pinhole break-off point so that trimming of the cast part is unnecessary.

United States Patent 1191 Hannes Dec. 17, 1974 [73] Assignee: Coats &Clark, Inc., New York,

[22] Filed: July 25, 1972 [21] Appl. No.: 274,910

52 11.5.01 164/347, 164/70, 164/131, 64/264z 12 4/3103, .6 ./.26 LQ/ 2l6 51 Im. c1 ..B22d 1/00 [58] Field of Search 164/113, 69, 303, 70, 347,164/347 US, 265, 264, 262, 131, 344, 404,

3,627,023 12/1971 Clark 164/264 Primary Examiner-J. Spencer OverholserAssistant Examiner-V. K. Rising 5 7 ABSTRACT Metal die casting apparatusincluding three abutting plates of which the outside plates are movablerelative to the center plate. The casting is formed in one plate and thegate for leading the molten metal to the casting is formed in the otherplates. After forming the casting, the gate is broken off and ejected bymovement of one end plate. The casting is then ejected by movement ofthe other end plate. The novel plate apparatus and the method ofdegating provides a pinhole break-off point so that trimming of the castpart is unnecessary.

8 Claims, 6 Drawing Figures 1 SELF CONTAINED METAL CASTING DIES BROADSTATEMENT OF INVENTION DESCRIPTION OF THE PRIOR ART In the prior art thecasting of metal parts is effected by injecting the molten metal from anozzle into a runner or gate that leads to the recess for forming thecast part. After casting, the part and the gate form an integral unit,and the gate has to be broken off before the cast part is furthertreated. The gate can be broken off by various procedures, such as aspecial tool or tumbling, but this results in a rough surface that mustbe later smoothed, trimmed or otherwise treated. Accordingly, it wouldbe desirable in metal casting to be able to break off the gate withoutthe necessity for the trimming or tumbling operation.

DESCRIPTION OF THE INVENTION The present invention provides a metal diecasting apparatus including three abutting die plates of which the outertwo are movable for separation of the attached gate from the cast part.

In the present invention metal die casting apparatus is provided whichincludes three abutting plates with the casting formed in one outerplate and the gate in the other two plates, separation of the gate fromthe cast part being effected by movement of one outer plate.

A further provision of the present invention isv a metal die castingapparatus having three abutting plates in which the cast part is formedin one plate and the other two plates are configured to provide aconical gate with a break-off tip.

There is further provided by the present invention a metal die castingapparatus having three abutting plates in which the cast part andattached gate are formed to be separately degated and ejected by pinssliding through the outside plates.

There is also provided in the present invention a method of metal diecasting in which plates are positioned in abutting relationship withinwhich a cast part and attached gate are formed, the part and gate beingseparately ejected by movement of the outer plates.

A further provision of the present invention is a method of metal diecasting in which abutting plates having a cast part and attached gateformed therein are sequentially moved relative to each other, and theplates include pins that slide therein to separately eject the cast partand the gate.

In a preferred embodiment of the die casting apparatus three plates areplaced in abutting position so that molten metal can be injectedtherein. One of the outside plates includes a recess in which the partis cast, and the center plate includes a through opening while the otheroutside plate includes another recess. The opening and the other recessform the gate during casting. Each of the outside die plates is movablerelative to the center plate. The opening in the center plate isconically shaped and tapers to a small opening at the end abutting therecess where the part is cast. After the molten metal solidifies, theoutside plate including part of the gate is moved away from the centerplate thereby breaking off the gate from the part. A pin is slidablymounted within this movable plate and projects therefrom so that when itstrikes a fixed part of the machine, the gate which has been broken offfrom the cast part is then ejected by the sliding ejection pin. It is tobe noted that the gate is conically formed tapering to its smallest sizewhere it contacts the cast part so that breakage is easily effected atthis contact point. Moreover, the part of the gate in the first movableplate is larger in size than the rest of the gate to insure that thebreakage occurs at the cast part. The other outside plate including thecast part is then moved relative to the center plate and includes asliding ejection pin that ejects the cast part when it strikes a fixedpart of the apparatus. This sequential ejection of the gate and castpart provides a pinhole break-off point and ejection of the part wherebytrimming in unnecessary.

A further provision of the present invention is a method of metal diecasting wherein three die plates are first placed in abutting relationso that molten metal injected therein will form a cast part in oneoutside plate and an attached gate that is partly within the insideplate and partly in the other outside plate, the gate within the centerplate being conically shaped and tapering toward the cast part. Theouter plate including part of the gate is then moved away from thecenter plate for degating causing the gate to break off from the castpart at the small conical tip, and a sliding ejection pin then knocksthe gate out of the die plate. Subsequently, the other outside die plateincluding the cast part is moved relative to the center plate and asliding pin mounted therein operated to eject the cast part from the dieplate.

The nature of the present invention will become more clearly apparentand better understood from the following description and accompanyingdrawings in which:

FIG. 1 is a front elevational view illustrating a die cast element andits attached gate as formed by a prior art procedure;

FIG. 2 is a schematic view, partly in section, showing the die plates ofthe present invention in abutting relation;

FIG. 3 is a view similar to FIG. 2 showing a displaced movement of oneof the die plates;

FIG. 4 is a view similar to FIG. 3 showing a further step in theoperation of the present invention;

FIG. 5 is a view similar to FIG. 3 showing a displacement of the otheroutside die plate; and

FIG. 6 is a view of the gate formed in the present invention.

In FIG. 1 a cast part 10 is shown which may be a metal slider element ofa zipper. In the prior art when this slider is die cast of metal, themolten metal is introduced to a runner or gate 12 which has a fan-shapedpart 14 where the metal flows into the mold or recess forming cast part10. After solidification, cast part 10 is thereby attached to gate 12,and it is necessary to degate part 10. This has been done in the priorart by a special tool or by tumbling the assembled part and attachedgate, but it is then necessary to trim part 10 since the surface isrough where fan-shaped part 14 breaks off.

In the present invention as shown in FIGS. a5 a novel arrangement of dieplates and method of degating is presented resulting in an improvedbreak-off arrangement so that trimming is no longer necessary. It isunderstood that the die casting apparatus would include the usualsupport with a power drive and cam actuation to provide for the movementof the parts. Since such elements are all conventional, they are notshown for purposes of clarity, and only the novel die plates andassociated features are illustrated.

Three die plates constitute the primary novel feature and includes acenter plate 16 which is substantially fixed with respect to theapparatus and outside plates 18 and 20 which are relatively movable withrespect to center plate 16. In FIG. 2 the die plates are shown in thenormal casting position in abutting relation with the recesses andopening described hereinafter ready to receive for the injection of themolten metal, such as zinc. Outside plate 20 is shown as a first dieplate and includes a first recess 22 which is formed on the sideabutting center plate 16 and in which the cast part is formed. A slidingejection pin 24 is mounted within plate 20 and located so that it canslide into recess 22.

Center plate 16 includes a through opening 26 which is generallyconically shaped. One end includes a small opening 28 in alignment withthe approximate center of recess 22 and enlarging therefrom at apredetermined conical angle for approximately Va of the thickness ofplate 16. Opening 28 continues to enlarge therefrom at a smaller angleand terminates in enlarged opening 30 at the'other end of plate 16 whereit abuts plate 18.

Outside plate 18 includes a second recess 32 having a specialconfiguration and generally aligned with opening 30. The configurationof recess 32 has a transverse dimension parallel to the surface of plate18 which is greater than the corresponding transverse dimension ofopening 30. As shown in FIG. 2 a top surface of recess 32 extendsgenerally perpendicular to the surface and continues on to form aconcave curved portion 34 of the plate to connect with a base surface36. It is understood that concave curve 34 extends around theperipheryof recess 32 which is generally circular in shape, and a convexcurved portion 38 of the plate 18 connects the lower part of base curve34 with the outer abutting edge as shown in FIG. 2. This convexcurvature 38 is an important feature of the invention, and although theexact curvature is not critical, it must be of a convex nature as willbe explained hereinafter.

As shown in phantom at the top of FIG. 2, a nozzle 40 injects moltenmetal into a conduit 41 thereby forming a runner 42 (see FIG. 4) so thatthe molten metal flows into opening 26 and recesses 22 and 32.

As seen in FIG. 3, a cast part 44 has been formed in recess 22. Anattached gate 46 was formed by the molten metal with part of the gate ininner plate 16 and part of the gate in outer plate 18. Originally castpart 44 is formed integral with gate 46, but FIG. 3 shows a step in thebreaking off of gate 46. As a feature of the present invention, theouter plate 18 is first moved in a direction perpendicular to thesurface of plate 16 and away from fixed plate 16 to the position shownin FIG. 3. Since the attaching connection between part 44 and gate 46 issmaller than any other part of gate 46, breakoff occurs at the abutmentof plates 16 and 20. This can be considered a pinhole break-off pointsince the opening 28 is sufficiently small so that the break-off leavesa small-mark in the nature of a pinhole that does not require trimmingas in the prior art. In fact, it is possible to design the location ofthe opening 28 so that the attachment of cast part 44 and gate 46 occursat a re cessed area, the pinhole marking being scarcely visible andcausing no problem as to any rough surface.

Plate 18 includes a pin 33 slidable therein that is positioned in thecasting position shown in FIG. 2 to have one end abutting recess 32. InFIG. 3 plate 18 has been moved to the right and it will be noted thatejection pin 33 is approaching a fixed part 48 of the apparatus. Pin 33is mounted so that it can slide within gate 18, and in FIG. 4 pin 33 isseen to strike a fixed part 48 whereby it is slid into recess 32 toeject gate 46. In FIG. 4 gate 46 is in the process of being ejected tofall into the space between plates 16 and 18.

In FIG. 5 the next step of the operation is shown where outer plate 20is moved to the left relative to fixed center plate 16. An ejection pin24 is mounted to slide within plate 20 in the same manner as pin 33 ismounted in plate 16. Accordingly, when pin 24 strikes a fixed part 50 ofthe apparatus, the end of pin 24 slides into recess 22 so that die castpart 44 is ejected therefrom and falls into the space between plates 16and 20.

From the above description it is clear that a sequence of steps providesthe novel method features of the invention, and the plate arrangementwith the novel configuration thereof provides the gate with the pinholebreak-off point. The gate itself is formed in a particular configurationas shown most clearly in F Ig. 6 so that the movement of die plate 18allows the desired break-off and particular ejection to take place.

As mentioned previously part of gate 46 is formed in the center dieplate 16 and part of the gate is formed in movable outer plate 18. Sincerecess 26 has larger end 30 opposite smaller end 28 which abuts recess22, gate 46 is formed with a generally conical shape having a tip 52 ofsmallest size as compared to the rest of gate 46 and therefore theweakest strength to insure that breakage will occur at that tip pointwhen die plate 18 is moved away from die plate 16. Since recess 32 has alarger transverse dimension, an undercut portion 54 is formed as part ofgate 46. An intermediate area 56 between end 52 and undercut portion 54provides a change in the angular conical form. A greater angle isprovided between end 52 and intermediate area 56, and a smaller conicalangle is provided from area 56 to undercut portion 54.

A critical feature of the invention is a concave area 58 in the gatethat is formed due to convex surface 38 in die plate 18. The large orhead area of gate 46 includes rounded surface 60 formed by the curvedsurface 34.

Since the concave area 58 is held in plate 18, and since point 52 is ofsuch small size, it is clear that movement of die plate 18 to the right(FIG. 3) will cause gate 46 to be broken off at point 52 and be retainedwithin die plate 18 as shown in FIG. 3.

A further important feature of the invention is the location of slidingpin 33 in the upper part of recess 32 as shown in FIG. 2. When one endof pin 33 strikes fixed part 48, the other end is caused to strike anupper part of gate 46 remote from concave area 58. This is shown inphantom in FIG. 6. Since pin 33 strikes this upper part of gate 46, apivoting action by gate 46 takes place on curved surface 38, and thegate 46 is ejected in a pivotal manner from die plate 18 as indicated bythe arrow 62 in FIG. 4.

The above description is a preferred embodiment of the subject novel diecasting apparatus for forming and ejecting metal parts so that trimmingis not necessary. Further modification is possible within the scope ofthe invention. For example, the die cast part may be formed with part inplate 20 and part in plate 16. In such case the draft angle would bedifferent in the plates to insure that the die part would be retained inplate 20 upon the movement away from fixed plate 16. Correspondingmodification would then be made in the through opening 26. It is alsopossible to change the shape of gate 46 as long as the smallest orpinhole point is retained at the end attached to the cast part and aconcave portion is provided at the other end to provide for a retentionwithin the movable plate and then for pivotal ejection.

It will be understood that still further changes and modifications maybe made by those skilled in the art in the particular features of theapparatus and method which has been described above for illustrativepurposes without departing from the scope of the invention as defined bythe following claims.

What I claim is:

1. Die casting apparatus having a plurality of die plates for forming ametal cast part and attached gate part therein comprising a first outerdie plate having a first recess in which said cast part is formed byinjecting molten metal therein;

a second die plate positionable in abutment with said first die plateduring casting and having an opening therethrough in communication withsaid first recess to permit said molten metal to flow through saidopening into said first recess;

said second die plate being mounted in a substantially fixed positionwithin said apparatus, and said first die plate being movable withrespect thereto;

a third outer die plate having a second recess therein,

said second recess and said opening in communication with each otherwhen said second and third plates are in abutment and adapted to formthe gate part when the molten metal is injected therein, said thirdplate being in abutment with said second plate during casting and beingmovable relative thereto,

said second recess being open at the surface of said third die plate andincluding at one end a portion which extends beyond the area of therecess open at the surface of the third die plate and thus constitutesan undercut portion of said third die plate, said undercut portionincluding a convex surface extending inwardly from the surface of thethird die plate and terminating at a concave surface portion of saidthird die plate within said second recess, said convex and concavesurface portions being shaped to permit removal of said gate part onlyby pivotal movement about said convex surface portion; and means mountedon said first and third plates for ejecting said cast part and said gatepart respectively from said die plates. 2. Die casting apparatusaccording to claim 1 in which said opening has an enlarged end on thatpart of said second die plate abutting said third die plate, and

the end of said opening abutting said first die plate is substantiallysmaller than said enlarged end.

3. Die casting apparatus according to claim 2 in which the surface ofsaid opening is substantially coneshaped.

4. Die casting apparatus according to claim 2 in which said secondrecess has a dimension across the face of said third die plate abuttingsaid second die plate that is greater than the dimension of saidenlarged end of said opening adapted to be aligned therewith.

5. Die casting apparatus according to claim 1 in which said ejectingmeans comprise pins slidably movable within said first and third platesto accomplish the ejection when said die plates move away from saidsecond plate and said pins contact a fixed portion of the apparatus.

6. A die casting apparatus for forming a metal cast part and attachedgate part therein, comprising: a dirst die member provided with asurface, a second die member provided with first and second oppositesurfaces, and a third die member provided with a surface, a first recessin said first die member extending to said surface thereof, said firstrecess being shaped to form said cast part, an opening in said seconddie member extending between said first and second opposite surfacesthereof, and a second recess in said third die member extending to saidsurface thereof, siad die members being movable to a casting positionwith the first surface of said second die member abutting said surfaceof said first die member and the second surface of said second diemember abutting said surface of said third die member with said firstand second recesses in communication by way of said opening, saidopeningand said second recess forming a recess for said gate part, a dimensionof said opening in the plane of said second surface being larger thanthe dimension thereof in the plane of said first surface, and adimension of said second recess in the plane of said surface of saidthird die member being greater than the corresponding dimension of theopening in the plane of said second surface, said second recess beingopen at the surface of said third die member and including at one end aportion which extends beyond the area of the recess open at the surfaceof the third die member and thus constitutes an under cut portion ofsaid third die member, said undercut portion including a convex surfaceextending inwardly from the surface of the third die member, andterminating at a concave surface portion of said third die member withinsaid second recess, said convex and concave surface portions beingshaped to permit removal of said gate part only be pivotal movementabout said convex surface portion, whereby cast metal breaks at saidfirst surface upon separation of said first and second die parts andwhereby said gate part is retained in said second recess upon relativeseparation of said second and third die members, and means for ejectingsaid cast part and said gate part from said first and third die membersrespectively.

7. The apparatus of claim 6 wherein said means for ejecting said gatepart from said third die member comprises a pin mounted in said thirddie member to slidably extend through said third die member into saidsecond recess for pivotally ejecting said gate part about said convexportion.

8. The apparatus of claim 7 wherein said pin extends through said thirddie member offcenter of said second recess on the side thereof away fromsaid convex portion.

I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,854,521 Dated December 17, 1974 Inventor(s) KARL I-IANNES It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, line l, after "METAL" add DIE Column 2, line 66, change "a-Sto 2 5 Column 6, line 18, change "dirst" to first line 27, change "siad"to said Signed and sealed this 10th day of June 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officerand Trademarks

1. Die casting apparatus having a plurality of die plates for forming ametal cast part and attached gatE part therein comprising a first outerdie plate having a first recess in which said cast part is formed byinjecting molten metal therein; a second die plate positionable inabutment with said first die plate during casting and having an openingtherethrough in communication with said first recess to permit saidmolten metal to flow through said opening into said first recess; saidsecond die plate being mounted in a substantially fixed position withinsaid apparatus, and said first die plate being movable with respectthereto; a third outer die plate having a second recess therein, saidsecond recess and said opening in communication with each other whensaid second and third plates are in abutment and adapted to form thegate part when the molten metal is injected therein, said third platebeing in abutment with said second plate during casting and beingmovable relative thereto, said second recess being open at the surfaceof said third die plate and including at one end a portion which extendsbeyond the area of the recess open at the surface of the third die plateand thus constitutes an undercut portion of said third die plate, saidundercut portion including a convex surface extending inwardly from thesurface of the third die plate and terminating at a concave surfaceportion of said third die plate within said second recess, said convexand concave surface portions being shaped to permit removal of said gatepart only by pivotal movement about said convex surface portion; andmeans mounted on said first and third plates for ejecting said cast partand said gate part respectively from said die plates.
 2. Die castingapparatus according to claim 1 in which said opening has an enlarged endon that part of said second die plate abutting said third die plate, andthe end of said opening abutting said first die plate is substantiallysmaller than said enlarged end.
 3. Die casting apparatus according toclaim 2 in which the surface of said opening is substantiallycone-shaped.
 4. Die casting apparatus according to claim 2 in which saidsecond recess has a dimension across the face of said third die plateabutting said second die plate that is greater than the dimension ofsaid enlarged end of said opening adapted to be aligned therewith. 5.Die casting apparatus according to claim 1 in which said ejecting meanscomprise pins slidably movable within said first and third plates toaccomplish the ejection when said die plates move away from said secondplate and said pins contact a fixed portion of the apparatus.
 6. A diecasting apparatus for forming a metal cast part and attached gate parttherein, comprising: a dirst die member provided with a surface, asecond die member provided with first and second opposite surfaces, anda third die member provided with a surface, a first recess in said firstdie member extending to said surface thereof, said first recess beingshaped to form said cast part, an opening in said second die memberextending between said first and second opposite surfaces thereof, and asecond recess in said third die member extending to said surfacethereof, siad die members being movable to a casting position with thefirst surface of said second die member abutting said surface of saidfirst die member and the second surface of said second die memberabutting said surface of said third die member with said first andsecond recesses in communication by way of said opening, said openingand said second recess forming a recess for said gate part, a dimensionof said opening in the plane of said second surface being larger thanthe dimension thereof in the plane of said first surface, and adimension of said second recess in the plane of said surface of saidthird die member being greater than the corresponding dimension of theopening in the plane of said second surface, said second recess beingopen at the surface of said third die member and including at one end aportion which extends beyond tHe area of the recess open at the surfaceof the third die member and thus constitutes an under cut portion ofsaid third die member, said undercut portion including a convex surfaceextending inwardly from the surface of the third die member, andterminating at a concave surface portion of said third die member withinsaid second recess, said convex and concave surface portions beingshaped to permit removal of said gate part only be pivotal movementabout said convex surface portion, whereby cast metal breaks at saidfirst surface upon separation of said first and second die parts andwhereby said gate part is retained in said second recess upon relativeseparation of said second and third die members, and means for ejectingsaid cast part and said gate part from said first and third die membersrespectively.
 7. The apparatus of claim 6 wherein said means forejecting said gate part from said third die member comprises a pinmounted in said third die member to slidably extend through said thirddie member into said second recess for pivotally ejecting said gate partabout said convex portion.
 8. The apparatus of claim 7 wherein said pinextends through said third die member offcenter of said second recess onthe side thereof away from said convex portion.